The British may waste more food than any other nation, throwing out 30-40% of all the produce they buy and grow each year, according to research. Figures collated from the government, supermarkets, processors and farmers show that modern food production methods may appear efficient, "but the reality is that large-scale manufacturing and rigid supply chains are creating very significant quantities of waste".

It is estimated that the wasted food is worth between £8bn and £16bn a year.

"The food sector now accounts for over a third of all the waste produced in the UK, a total of 17m tonnes," says the research, by C-Tech Innovation, a manufacturing consultancy. "About 15% arises from food manufacturing and a further 21% from distribution, retailing and consumption."

It notes that US food wastage is running behind Britain at about 25%, and that 4 million people in the UK "cannot afford a healthy diet and that one in seven people over 65 are at serious risk of malnourishment".

Separate government figures show that some 17m tonnes of food worth up to £20bn a year are being put into landfill, even though approximately 25% of it could be safely eaten by people or animals, or turned into compost and energy. The cost of transporting it and throwing it into landfills is thought to be more more than £175m a year.

Guardian research, backed by BBC Radio 4's Costing the Earth programme broadcast last night, suggests the increasing amount of food waste - thought to be rising roughly 15% a decade - is being experienced across the whole food chain from the field to the house.

"It is increasing at a phenomenal rate. We are buying more, but we are also abdicating responsibility, too. It's easy to let the food industry tell us what to do," said the food charity FairShare, which collects surplus - but edible - food from hundreds of canteens, retailers, supermarkets, manufacturers and restaurants, and distributes 2,000 tonnes of food a year to voluntary groups, who feed more than 12,000 old and otherwise vulnerable people a day.

FairShare has estimated that the edible food thrown away could feed more than 250,000 people. "We could easily increase what we collect and distribute," said a spokesman yesterday.

The waste starts with farmers, who are frequently forced to plough up or dispose of large amounts of perfectly good fruit and vegetables because of rigid contracts with processors or retailers. These usually specify the size and shape of fruits and vegetables, and the exact number needed.

"If you have even a small increase of temperature, you may see a 10-20% increase in crop yields," said Phil Hudson of the National Farmers Union.

"There may, however, be no home for this food because of extremely tight programmes by the industry. Some years ago, the extra food produced might have gone to wholesalers, but this market is now only about 15% of the total, and it cannot take surpluses."

Consumers were also largely responsible for wastage, said Mr Hudson. "We now always look for a specific size and shape of food in supermarkets. Anything outside that is left on the shelf. But is this human nature or are we being conditioned by retailers to look for this? We have certainly created a level of expectation which encourages large scale waste."

A recent report for Prudential Insurance, based on a survey of more than 1,000 households, found that 61% of people admit throwing out at least one bag of salad each week without even removing the packaging. A similar percentage threw away unused loaves of bread and fruit, while slightly fewer threw out milk, cheese and meat. Also regularly wasted were prepared meals.

According to Biffa, one of the largest waste handlers in Britain, households now throw out more than supermarkets and the food processing industry combined. Food waste is roughly one third by weight of all the waste produced by households.

"People just buy more than they can eat," said Peter Jones, a Biffa director.

"We estimate that each family now throws out about 2.7kg (6lb) of food per person per week," said East London Community Recycling Partnership, which collects and monitors the food waste of thousands of households on several housing estates and then composts it before giving it back to people for window boxes, allotments and garden use.

"The amount of food being wasted is increasing all the time," said Cam Matheson, who runs the East London scheme. "We are not allowed to sell it, because of animal byproducts, but composting like this could easily be extended to every housing estate in Britain."

The food manufacturing industry, which prepares convenience foods, sandwiches, tinned food and processed food, throws away at least 1m tonnes a year, Mr Jones said. New regulations which apply to anyone handling food for humans or animals are also encouraging the food industry to reject food, he said.

According to Biffa, supermarkets and other retailers throw out about 500,000 tonnes of food a year, of which only a small proportion goes to charities. Supermarkets are reluctant to say how much food is wasted, but it is possible to estimate from information put on their websites and in annual reports.

Tesco, which dominates British food retailing, says it sent 131,000 tonnes of waste to landfill in 2004, of which "the majority was food". Sainsbury's, which distributes surplus food to more than 400 charities, says it sent 91,000 tonnes to landfills, of which at least 70,000 tonnes is believed to be waste food. Most retailers say they have significantly reduced the amount of food wasted each year since 2000.

Better storage and distribution of food by supermarkets has reduced the amount of waste to only about 0.5% a year, industry sources say, but the total tonnage is enormous. The Environment Agency has estimated that the food and drinks industry generates 10% - about 10m tonnes - of the total waste produced by all industrial and commercial activity in the UK.

"A very few people remember rationing, but most of us have no idea what it is like not to have enough food," said Jeanette Longfield, coordinator of Sustain, a group of more than 100 food, environmental and other charities and unions. "The only justification for chucking stuff is because it is unsafe. We don't know how it is produced so they chuck it out without thinking."

Where it goes

Supermarkets: Up to 500,000 tonnes may be wasted each year, mostly because it is approaching its sell-by date. Some supermarkets make food available to charities and more composting is done. But the majority is landfilled, the cheapest option, in its packaging. In future it will be illegal to landfill any food derived from meat. This will encourage incineration.

Households: Up to a third of food bought may be wasted because we buy too much and do not plan menus. Much is discarded when it is near its sell-by date and people no longer eat everything on their plate. Processed food is increasingly rejected before it has been unpacked. Less is composted as most food is processed and vegetable growing has declined.

Farmers: Some 30%-40% by weight of all food grown can be lost. Retailers and food processors demand unblemished, specifically sized, shaped and coloured food. Bumper crops resulting from high temperatures cannot always find a market because of the declining wholesale trade . Food is usually ploughed back in to the fields.